Of the roughly 500 detainees held at the U.S. prison camp at Guantanamo Bay, Cuba, none is more notorious than Mohammad al-Qahtani, the so-called "20th hijacker." Only weeks before 9/11, he tried to enter the U.S. illegally in Orlando, Fla., while the plot's leader, Mohammad Atta, waited to pick him up in the airport parking lot. As the Pentagon has said, "Had al-Qahtani succeeded in entering the U.S., it is believed he would have been on United Airlines Flight 93, the only hijacked aircraft that had four hijackers instead of five [and the one that ended up crashing in a Pennsylvania field instead of striking the White House, its widely believed intended target]."

A secret document gives an inside look at how detainees at Guantanamo are treated

TIME EXCLUSIVERead the Complete Interrogation Log:From the TIME Archive

Last June, TIME published excerpts from a highly classified, 84-page log minutely detailing al-Qahtani's interrogation at Guantanamo. Now, as an increasing number of detainees mount legal challenges to their incarceration, TIME is making the record of al-Qahtani's treatment available to the public in its entirety (except for some names which have been redacted) for the first time. Back in June 2005, the Pentagon insisted that al-Qahtani had provided vital intelligence, focusing on key al-Qaeda leaders and some 30 fellow prisoners at Guantanamo whom he identified as Osama bin Laden's bodyguards.

Now, in an eyewitness account of al-Qahtani at Guantanamo, his recently appointed American lawyer tells TIME that al-Qahtani has repudiated all of his previous statements  claiming they were extracted under brutal torture. And that repudiation is sure to fuel the growing number of challenges in American courts from the detainees at Guantanamo whom al-Qahtani fingered.

For most of his confinement at Guantanamo, al-Qahtani, like other "enemy combatants," has been in legal limbo, never charged with a crime, unrepresented by legal counsel and without any recourse to U.S. courts. But a source has told TIME that last year his father in Saudi Arabia approached the Center for Constitutional Rights, a New York-based nonprofit organization, which has provided al-Qahtani with a lawyer.

That lawyer, Gitanjali S. Gutierrez, a CCR staff attorney, has already filed a challege in federal court, in the District of Columbia, to al-Qahtani's detention. She has also visited him twice at Guantanamo, first in December 2005 and again in January of this year. After spending more than 30 hours talking with him through an interpreter, she told TIME that al-Qahtani today appears to be a broken man, fearful and at times disoriented  someone who has "painfully described how he could not endure the months of isolation, torture and abuse, during which he was nearly killed, before making false statements to please his interrogators."

When al-Qahtani got off his plane in Orlando in August 2001, he was refused entry to the U.S., deported, and captured in Afghanistan only a few months after 9/11  as Osama bin Laden fled his mountain sanctuary at Tora Bora. Al-Qahtani was then brought to Guantanamo where, according to the Pentagon, he admitted that he had been sent to the U.S. by Khaled Sheik Mohammed, architect of the 9/11 attacks, and that he had met Osama bin Laden on several occasions. Al-Qahtani also confirmed that he had received terrorist instruction at two al-Qaeda training camps and met with numerous senior al-Qaeda leaders.

But from the standpoint of cases currently under review in U.S. federal courts, al-Qahtani's most significant disclosure was informing on some 30 fellow Guantanamo prisoners. The Pentagon quickly used his statements about those prisoners before special military tribunals to justify their indefinite detention as "enemy combatants."

Lawyers for detainees fingered by al-Qahtani strenuously object to that evidence. And a growing number are challenging the government, claiming that al-Qahtani's information was extracted under torture and is, therefore, unreliable and inadmissible in court.

But in a major case in the U.S. Court of Appeals for the District of Columbia to be argued on March 22  a case that many observers believe will ultimately end up in front of the Supreme Court  the government is expected to argue that the reliability of statements like al-Qahtani's should not even be considered.

Instead, government lawyers will seek to apply the Detainee Treatment Act, a controversial December 2005 law sponsored by Senator Lindsay Graham of South Carolina, that would preclude extensive court review of Guantanamo detentions. The Detainee Treatment Act says that habeas corpus  the right of prisoners to have their detention legally justified to a U.S. court  does not apply to Guantanamo prisoners except on appeal. Detainee lawyers argue that the provision clashes with a 2001 Supreme Court ruling that opened the federal courts to any detainee held by the United States anywhere in the world.

Questions surrounding the Detainee Treatment Act will also come before the Supreme Court on March 28, when lawyers for Salim Ahmad Hamdan, Osama bin Laden's alleged driver, challenge government attempts to put him on trial before a military commission. "The issue in this court case is critically important because if the government has its way, Guantanamo will be returned to a legal black hole," contends Eric M. Freedman, a professor of constitutional law at Hofstra University and legal consultant to detainees, though not al-Qahtani. "It would be an outrage if evidence being used to hold prisoners was extracted by unconscionable methods and that fact did not come to light in a court of law." For the Pentagon's part, a spokesperson told TIME that "it is longstanding Department of Defense policy to treat all detainees humanely." The detailed interrogation log of al-Qahtani seems to make clear that at the very least that policy has not always been followed and that the definition of humane treatment is up for debate.